Erythromycin belongs to the class of medications known as macrolide antibiotics. It is used to treat infections caused by certain types of bacteria.

It is most commonly used to treat the following:

• lower respiratory tract infections such as pneumonia, whooping cough, diphtheria, and Legionnaires' disease
• skin infections (including acne)
• sexually transmitted infections such as syphilis and chlamydia
• upper respiratory infections such as sinusitis and pharyngitis

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

Adults: The usual recommended adult dose of erythromycin ranges from 250 mg to 500 mg 4 times daily (when taken by mouth). The maximum daily dose is 4 g.

The exact dose and the length of treatment depends on the condition being treated. Erythromycin base works best on an empty stomach (at least 30 minutes before or 2 hours after meals), but if stomach problems occur, talk to your doctor or pharmacist about taking the medication with food.

Children: Doses for children depend on their age, weight, and the condition being treated.

Finish all of this medication, even if you start to feel better.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Each oval, pink, biconvex, film-coated tablet, identified "250", contains erythromycin base 250 mg. Nonmedicinal ingredients: colloidal silicon dioxide, croscarmellose sodium, magnesium stearate, microcrystalline cellulose, stearic acid, carnauba wax, D&C Red No. 30 Aluminum Lake, hydroxypropyl methylcellulose 2910 E5, polyethylene glycol 3350, and titanium dioxide.

Do not take this medication if you:

• are allergic to erythromycin or any ingredients of the medication
• are taking astemizole*, terfenadine, cisapride, pimozide, ergotamine, or dihydroergotamine
• have an infection that is caused by bacteria that is known to be resistant to erythromycin

*Astemizole, terfenadine, and cisapride are no longer marketed in Canada.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal or stomach cramping and discomfort
• diarrhea
• nausea or vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• confusion
• continued diarrhea even after you have finished taking this medication
• hallucinations
• irregular or fast heartbeat
• loss of hearing (temporary)
• skin rash, redness, or itching
• stomach pain (severe)
• symptoms of liver damage (e.g., yellow skin or eyes, abdominal pain, dark urine, clay-coloured stools, loss of appetite, nausea and vomiting, or itching)
• unusual tiredness or weakness
• vertigo (dizziness, problems with balance)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• seizures
• severe watery or bloody diarrhea
• symptoms of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen)
• symptoms of a serious allergic reaction (e.g., swelling of the face or throat, hives, or difficulty breathing)
• symptoms of a severe skin reaction (e.g., peeling or blistering skin)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic reactions: Before you take erythromycin base, inform your doctor about any previous adverse reactions you have had to medications, especially azithromycin or clarithromycin. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing or swelling of the face and throat.

Bacterial resistance: Misuse of an antibiotic such as erythromycin may lead to the growth of resistant bacteria that will not be killed by the antibiotic. If this happens, the antibiotic may not work for you in the future. Although you may begin to feel better early in your course of treatment with erythromycin, you need to take the full course exactly as directed to finish ridding your body of the infection and to prevent resistant bacteria from taking hold. Do not take erythromycin or other antibiotics to treat a viral infection such as the common cold; antibiotics do not kill viruses, and using them to treat viral infections can lead to the growth of resistant bacteria.

Diarrhea: This medication is associated a serious infection called Clostridium difficile associated diarrhea, caused by the bacteria C. difficile. This can occur as late as 2 months after your last dose of this medication. If you have loose, watery bowel movements that are green, foul-smelling, or bloody that may be accompanied by fever after taking erythromycin, get medical attention as soon as possible.

Heart rhythm:  Erythromycin base has been linked to changes to the normal rhythm of the heart, including an irregular heartbeat called QT prolongation. If you are at risk for heart rhythm problems (e.g., people with heart failure, angina, low potassium or magnesium levels), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver problems: People with reduced liver function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

There have been reports of liver problems occurring in a small percentage of people taking erythromycin products, particularly erythromycin estolate. Anyone experiencing yellowing of the pigments of their eyes or skin (suggestive of jaundice) should see their doctor.

Myasthenia gravis: Use of this medication may aggravate this condition.

Overgrowth of organisms: Prolonged or repeated use of erythromycin may result in an overgrowth of bacteria or fungi and organisms that are not killed by the medication. This can cause problems such as yeast infections.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking erythromycin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety of erythromycin for use by newborns has not been established.

There may be an interaction between erythromycin base and any of the following:

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.